1. Field of the Invention
This invention relates to a method of examining insulation displacement connection, for example, in the production of a wire harness, and also relates to an apparatus for performing this method.
2. Description of the Related Art
As shown in FIG. 7, a wire harness, for example, comprises parallel wires 50 each having a conductor 51 coated with an insulating resin 52, connectors 30 connected to the wires 50 at suitable regions in a lengthwise direction and a widthwise direction, and covers 31 attached to the respective connectors 30 if necessary. In view of the efficiency of the operation, insulation displacement fitting connection (hereinafter referred to as "insulation displacement connection") as shown in FIG. 8 has now been increasingly used for connecting the wires 50 to the connector 30.
As shown in FIG. 8, in this insulation displacement connection, a vertically-movable, insulation displacement connecting blade holder (not shown), having insulation displacement connecting blades 10 corresponding respectively to the wires 50, is moved downward, and a distal end surface of each insulation displacement connecting blade 10 press-fits the associated wire 50 into slots 41a of an associated insulation displacement connecting terminal 40 of the connector 30, so that the wire is held in the terminal 40 by pinching, produced in the terminal 40 at this time, and hence is connected to the terminal. During this press-fitting operation, the insulating sheath 52 is cut by inner edges of the slots 41a, so that the conductor 51 in the insulating sheath 52 is brought into contact with the inner edges of the slots 41a, thereby making an electrical connection between the conductor 51 and the insulation displacement connecting terminal 40.
Examples of defective insulation displacement connection, developing during the above insulation displacement connecting operation, are as follows.
For some reason, if any of the wires, fed to the insulation displacement connecting step, is inserted in a twisted condition into the slots to be insulation-displacement-connected to the terminal, the wire can be press-fitted excessively or inadequately. Also, there is a possibility that the wire fails to be inserted into the slots, and the empty hitting occurs, so that a wire-absent condition develops. Alternatively, there can be encountered abnormal insulation displacement connection in which the wire to be inserted into the adjoining cavity is inserted, together with the proper wire, into one slot, so that the double wire-hitting occurs.
In the conventional insulation displacement connection examination, it is judged that the insulation displacement connection is finished when the insulation displacement connecting blade for press-fitting the wire into the slots, reaches its lower dead point. With this method, however, the above deficiencies can not be detected.
For example, in the case of "wire absence", the insulation displacement connecting blade reaches the lower dead point without undergoing any resistance, and even in the case of the abnormal insulation displacement connection (double wire-hitting), the insulation displacement connecting condition is not different from the proper insulation displacement connecting condition for one wire if the wires are soft, and if the force for pressing the insulation displacement connecting blade is extremely large.